• Title/Summary/Keyword: Residual elements

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Fast Matching Pursuit Method Using Property of Symmetry and Classification for Scalable Video Coding

  • Oh, Soekbyeung;Jeon, Byeungwoo
    • Proceedings of the IEEK Conference
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    • 2000.07a
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    • pp.278-281
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    • 2000
  • Matching pursuit algorithm is a signal expansion technique whose efficiency for motion compensated residual image has already been demonstrated in the MPEG-4 framework. However, one of the practical concerns related to applying matching pursuit algorithm to real-time scalable video coding is its massive computation required for finding dictionary elements. In this respective, this paper proposes a fast algorithm, which is composed of three sub-methods. The first method utilizes the property of symmetry in 1-D dictionary element and the second uses mathematical elimination of inner product calculation in advance, and the last one uses frequency property of 2-D dictionary. Experimental results show that our algorithm needs about 30% computational load compared to the conventional fast algorithm using separable property of 2-D gabor dictionary with negligible quality degradation.

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Influence of Heat Treatment on the Structures and Mechanical Properties of Cast Irons. (주철(鑄鐵)의 열처리조건(熱處理條件)에 의한 조직(組織) 및 기계적(機械的) 성질(性質)에 관(關)한 연구(硏究)(1))

  • Kim, Hong-Beom;Choi, Chang-Ock
    • Journal of Korea Foundry Society
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    • v.2 no.2
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    • pp.10-17
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    • 1982
  • This study has been carried out to determine the change of mechanical properties and microstructures by the heattreatment to relieve the residual stresses for gray cast irons. The results have been obtained from the experiment as follows; 1) The annealing above $600^{\circ}C$ for the stress relieving of gray cast iron decrease the tensile strength and hardness 2) The decrease reates of tensile strength and hardness of gray cast iron after annealing above $600^{\circ}C$ are increased with increasing the holding time. 3) The gray cast iron containing the elements of Mn, Cr has increased the heating temperature for the decrease of tensile strength and hardness. 4) The decrease of mechanical properties by annealing are assumed that the formation of ferrite takes placed from the decomposition of eutectoid cementite in the matrix.

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A Numerical Method for a High-Speed Ship with a Transom Stern

  • Kyoung Jo-Hyun;Bai Kwang-June
    • Journal of Ship and Ocean Technology
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    • v.8 no.3
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    • pp.8-17
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    • 2004
  • A numerical method is developed for computing the free surface flows around a transom stern of a ship at a high Froude number. At high speed, the flow may be detached from the flat transom stern. In the limit of the high Froude number, the problem becomes a planning problem. In the present study, we make the finite-element computations for a transom stern flows around a wedge-shaped floating ship. The numerical method is based on the Hamilton's principle. The problem is formulated as an initial value problem with nonlinear free surface conditions. In the numerical procedures, the domain was discretized into a set of finite elements and the numerical quadrature was used for the functional equation. The time integrations of the nonlinear free surface condition are made iteratively at each time step. A set of large algebraic equations is solved by GMRES(Generalized Minimal RESidual, Saad and Schultz 1986) method which is proven very efficient. The computed results are compared with previous numerical results obtained by others.

Plastic analysis of steel arches and framed structures with various cross sections

  • Silva, Jessica L.;Deus, Lidiane R.R.M.;Lemes, Igor J.M.;Silveira, Ricardo A.M.
    • Steel and Composite Structures
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    • v.38 no.3
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    • pp.257-270
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    • 2021
  • This paper presents a displacement-based numerical methodology following the Euler-Bernoulli theory to simulate the 2 nonlinear behavior of steel structures. It is worth emphasizing the adoption of co-rotational finite element formulations considering large displacements and rotations and an inelastic material behavior. The numerical procedures proposed considers plasticity concentrated at the finite elements nodes, and the simulation of the steel nonlinear behavior is approached via the Strain Compatibility Method (SCM), where the material constitutive relation is used explicitly. The SCM is also applied in determining the sections bearing capacity. Moreover, the present numerical approach is not limited to a specific structural member cross-sectional typology, with the residual stress models introduced explicitly in subareas of steel cross-sections generated by a 2D discretization. Finally, results consistent with the literature and with low processing time are presented.

High-Velocity Impact Damage Behavior of Carbon/Epoxy Composite Laminates

  • Kim, Young A.;Woo, Kyeongsik;Cho, Hyunjun;Kim, In-Gul;Kim, Jong-Heon
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.2
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    • pp.190-205
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    • 2015
  • In this paper, the impact damage behavior of USN-150B carbon/epoxy composite laminates subjected to high velocity impact was studied experimentally and numerically. Square composite laminates stacked with $[45/0/-45/90]_{ns}$ quasi-symmetric and $[0/90]_{ns}$ cross-ply stacking sequences and a conical shape projectile with steel core, copper skin and lead filler were considered. First high-velocity impact tests were conducted under various test conditions. Three tests were repeated under the same impact condition. Projectile velocity before and after penetration were measured by infrared ray sensors and magnetic sensors. High-speed camera shots and C-Scan images were also taken to measure the projectile velocities and to obtain the information on the damage shapes of the projectile and the laminate specimens. Next, the numerical simulation was performed using explicit finite element code LS-DYNA. Both the projectile and the composite laminate were modeled using three-dimensional solid elements. Residual velocity history of the impact projectile and the failure shape and extents of the laminates were predicted and systematically examined. The results of this study can provide the understanding on the penetration process of laminated composites during ballistic impact, as well as the damage amount and modes. These were thought to be utilized to predict the decrease of mechanical properties and also to help mitigate impact damage of composite structures.

Numerical Analysis of Two-Dimensional Nonlinear Radiation Problem Using Higher-Order Boundary Element Method (고차경계요소법을 이용한 2차원 비선형 방사문제의 수치해석)

  • Hong-G. Sung;Hang-S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.1
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    • pp.67-81
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    • 2000
  • An accurate and efficient numerical method for two-dimensional nonlinear radiation problem has been developed. The wave motion due to a moving body is described by the assumption of ideal fluid flow, and the governing Laplace equation can be effectively solved by the higher-order boundary element method with the help of the GMRES (Generalized Minimal RESidual) algorithm. The intersection or corner problem is resolved by utilizing the so-called discontinuous elements. The implicit trapezoidal rule is used in updating solutions at new time steps by considering stability and accuracy. Traveling waves caused by the oscillating body are absorbed downstream by the damping zone technique. It is demonstrated that the present method for time marching and radiation condition works efficiently for nonlinear radiation problem. To avoid the numerical instability enhanced by the local gathering of grid points, the regriding technique is employed so that all the grids on the free surface may be distributed with an equal distance. This makes it possible to reduce time interval and improve numerical stability. Special attention is paid to the local flow around the body during time integration. The nonlinear radiation force is calculated by the "acceleration potential technique". Present results show good agreement with other numerical computations and experiments.

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Rheological Properties of Rough Rice(I) -Stress Relaxation of Rough Rice Kernel- (벼의 리올러지 특성(特性)(I) -곡립(穀粒)의 응력이완(應力弛緩)-)

  • Kim, M.S.;Kim, S.R.;Park, J.M.
    • Journal of Biosystems Engineering
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    • v.15 no.3
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    • pp.207-218
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    • 1990
  • Grains display characteristics of both elastic bodies and viscous fluids when they are subjected to mechanical treatments in harvesting, handling, and processing. This viscoelastic behavior of grains when mechanically stressed must be fully understood to establish maximum machine efficiency and have a minimum degree of grain damage and the highest quality of the final product. The studies were conducted to examine the effect of the moisture content, the loading rate and the initial deformation on the stress relaxation behavior of whole kernel of rough rice, and develop the rheological model to represent its stress relaxation behavior. The following results were obtained from the study. 1. Moisture content had the greatest influence on the initial portion of the relaxation curve. With elapsing time the lower moisture content resulted in the lower residual stress for the Japonica-type rough rice and vice versa for the Indica-type rough rice. But within the ranges of moisture content tested, the degree of stress relaxation per unit strain on the Indica-type rough rice was a little higher than those on the Japonica-type rough rice. 2. The slower loading rate resulted in less initial stress. The decreasing trend of residual stress for all the samples tested with increasing loading rate was shown. 3. The higher initial deformation for all the samples resulted in less initial stress. The increasing of amount of stress relaxation per unit strain with increase of initial stress indicated that viscoelastic properties of rough rice depended not only upon duration of load applied but also initial stress applied. This means that rough rice is nonlinear viscoelastic material. 4. The compression stress relaxation properties of rough rice kernel can be described by a generalized Maxwell model representing by the Maxwell elements.

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The Effect of PWHT on Fracture Toughness in HAZ of Cr-Mo Steel(II) (Cr-Mo鋼 熔接熱影響部 의 破壞靭性 에 미치는 熔接後 熱處理 의 影響 II)

  • 임재규;정세희
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.1
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    • pp.40-46
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    • 1985
  • Some problems such as toughness decrement and stess relief cracking (SRC), many occur when post weld heat treatment (PWHT) is applied to remove residual stress adn hydrogen. In this paper PWHT was carried out under the stress of 0, 98, 196 and 294 MPa (0, 10, 20 and 30kgf/mm$^{2}$ each) to simulate residual stress in HAZ of Cr-Mo steel. The effect of applied stress during PWHT on fracture toughness was evaluated by COD fracture toughness test, micro-hardnes test and observation of SEM. The experimental results are as follows; (1) Fracture toughness of weld HAZ was improved by PWHT, but it decreased as heat treated under the stress. (2)Hardness ratio under the stress of 294MPa (30kg/mm$^{2}$) was lower and fracture toughness was decreased than that of the no stress. (3) Applied stress in weld HAZ during PWHT assisted precipitation of over saturated alloying elements in the structure, so fracture surface at the stress of 294MPa (30kg/mm$_{2}$) appeared the grain boundary failure possibly one of the reasons for PWHT embrittlenment.

Development of an Hazard Analysis Critical Control Point Application Model for a Olive Flounder (Paralichthys olivaceus) Aquaculture Farm (넙치 양식장 위해요소중점관리기준(HACCP) 적용모델 개발)

  • Kim, Tae-Jin;Min, Jin-Gi;Park, Sun-Mee;Choi, Jae-Suk;Lee, Myung Suk;Kim, Young-Mog;Chung, Yong-Hyun
    • Journal of Fisheries and Marine Sciences Education
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    • v.25 no.5
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    • pp.1055-1067
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    • 2013
  • We attempted to apply the HACCP system adopted in the food industry to a olive flounder (Paralichthys olivaceus) aquaculture farm to ensure the hygiene safety of farmed fish. In this study, HACCP system procedures, including HACCP team organization, critical point determination, establishment of standard limits etc., were established using Codex 12 procedures. To determine whether hazards were critical elements, we evaluated the likelihood and seriousness of each hazard element. The likelihood of residual medicine exceeding the acceptable limit in shipped fish products was demonstrated to be a critical hazard element. Management of the shipment stage was determined to be a critical control point (CCP). Checking the records for stock and release and maintaining a history of medicine use before shipping the fish were suggested as monitoring methods. The standards for acceptable residual medicine were set based on relevant laws and regulations, and then the limits were adapted and established for the CCP. An HACCP plan applicable to olive flounder farms was established.

Thermoelastic effect on inter-laminar embedded delamination characteristics in Spar Wingskin Joints made with laminated FRP composites

  • Mishra, P.K.;Pradhan, A.K.;Pandit, M.K.;Panda, S.K.
    • Steel and Composite Structures
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    • v.35 no.3
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    • pp.439-447
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    • 2020
  • This paper presents two sets of full three-dimensional thermoelastic finite element analyses of superimposed thermo-mechanically loaded Spar Wingskin Joints made with laminated Graphite Fiber Reinforced Plastic composites. The study emphasizes the influence of residual thermal stresses and material anisotropy on the inter-laminar delamination behavior of the joint structure. The delamination has been pre-embedded at the most likely location, i.e., in resin layer between the top and next ply of the fiber reinforced plastic laminated wingskin and near the spar overlap end. Multi-Point Constraint finite elements have been made use of at the vicinity of the delamination fronts. This helps in simulating the growth of the embedded delamination at both ends. The inter-laminar thermoelastic peel and shear stresses responsible for causing delamination damage due to a combined thermal and a static loading have been evaluated. Strain energy release rate components corresponding to the Mode I (opening), Mode II (sliding) and Mode III (tearing) of delamination are determined using the principle of Virtual Crack Closure Technique. These are seen to be different and non-self-similar at the two fronts of the embedded delamination. Residual stresses developed due to the thermoelastic anisotropy of the laminae are found to strongly influence the delamination onset and propagation characteristics, which have been reflected by the asymmetries in the nature of energy release rate plots and their significant variation along the delamination front.